Test: Biomolecules - 1 - NEET MCQ

Oils have lower melting point (e.g., gingely oil) and hence remain as oil in winters.

Topic in NCERT: Fats and oils (lipids)

Line in NCERT: "oils have lower melting point (e.g., gingelly oil) and hence remain as oil in winters."

The given molecule is adenylic acid. It is a nucleotide found in RNA. It is an ester of phosphoric acid with the nucleoside adenosine. It consists of a phosphate group, a pentose sugar ribose, and the nucleobase adenine.

Topic in NCERT: Nucleic acids

Line in NCERT: "living organisms have a number of carbon compounds in which heterocyclic rings can be found. some of these are nitrogen bases adenine, guanine, cytosine, uracil, and thymine. when found attached to a sugar, they are called nucleosides. if a phosphate group is also found esterified to the sugar they are called nucleotides. adenosine, guanosine, thymidine, uridine and cytidine are nucleosides. adenylic acid, thymidylic acid, guanylic acid, uridylic acid and cytidylic acid are nucleotides."

Proteins human haemoglobin consists of 4 subunits. Two of these are identical toeach other. Hence, two subunits of αα type and two subunits of ββ type together constitute the human haemoglobin (Hb).

Topic in NCERT: Structure of proteins

Line in NCERT: "adult human haemoglobin consists of 4 subunits."

The diagram shown is a uracil which is a pyramidine belonging to nitrogen bases.

Topic in NCERT: Nucleic acids

Line in NCERT: "living organisms have a number of carbon compounds in which heterocyclic rings can be found. some of these are nitrogen bases adenine, guanine, cytosine, uracil, and thymine. when found attached to a sugar, they are called nucleosides."

• Proteins are polymers of amino acids undergo dehydration to form a peptide linkage.
• Dipeptides are formed by a single peptide bond and a tripeptide through two peptide bonds and so on.

Topic in NCERT: Structure of proteins

Line in NCERT: "proteins, as mentioned earlier, are heteropolymers containing strings of amino acids."

Protein molecules get denatured due to high temperature, very high or low pH and high energy radiation but there is no effect due to high pressure.

Topic in NCERT: Temperature and ph

Line in NCERT: "high temperature destroys enzymatic activity because proteins are denatured by heat."

Topic in NCERT: Table 9.3 some secondary metabolites

Line in NCERT: "abrin, ricin"

Based on number of amino and carboxyl groups, there are acidic (e.g., glutamic acid), basic (lysine) and neutral (valine) amino acids. Similarly, there are aromatic amino acids (tyrosine, phenylalanine, tryptophan).

Topic in NCERT: Amino acids

Line in NCERT: "aromatic amino acids (tyrosine, phenylalanine, tryptophan)."

Uracil nitrogenous base is produces nucleoside only with ribose sugar. This nucleoside is present only inside the RNA and absent in DNA.

Topic in NCERT: Nitrogen bases

Line in NCERT: "uracil (pyrimidine)"

Enzymes have a particular optimum range of working temperature, below which their activity decreases.

Topic in NCERT: Temperature and ph

Line in NCERT: "low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat."

• Primary structure of protein is formed by peptide linkages between two amino acids.
• Secondary structure, i.e. α-Helix and β-Sheath, of protein is formed by hydrogen bonds.
• Tertiary structure of protein is formed by disulphide linkages between different amino acids
• Quaternary structure is formed when multiple chains of polypeptides held together by hydrogen bonds.

Topic in NCERT: Tertiary structure

Line in NCERT: "in addition, the long protein chain is also folded upon itself like a hollow woolen ball, giving rise to the tertiary structure (fig. 9.3 c)."

Plant cell walls are made of cellulose. Paper made from plant pulp is cellulose.

Topic in NCERT: Polysaccharides

Line in NCERT: "plant cell walls are made of cellulose."

Amino acids are organic compounds containing an amino group and an acidic group as substituents on the same carbon, i.e. the α-carbon. Hence, they are called α-amino acids.

Topic in NCERT: Amino acids

Line in NCERT: "amino acids are organic compounds containing an amino group and an acidic group as substituents on the same carbon i.e., the α-carbon."

Assertion (A): The formation of the enzyme-substrate complex is indeed a transient phenomenon and is crucial for catalysis, as it facilitates the reaction by bringing the substrate into proximity with the active site of the enzyme and lowering the activation energy. This is true.
Reason (R): The transition state structure is actually the least stable state, not the most stable state, during the conversion of substrate to product. The transition state is an intermediate, high-energy configuration that occurs before the substrate is converted into the product. This makes the Reason false.
Thus, the Assertion is true, but the Reason is false.

Topic in NCERT: Factors affecting enzyme activity

Line in NCERT: "the formation of the es complex is essential for catalysis."

- Statement i is correct because polysaccharides can indeed be classified as homopolymers (like cellulose, which is made only of glucose) or heteropolymers (which contain different types of monosaccharides).

- Statement ii is incorrect; while cellulose is a homopolymer of glucose, it does not form complex helical structures. Instead, it has a linear structure that forms microfibrils.

- Statement iii is correct; starch serves as an energy reserve in plants and forms helical structures that can bind iodine, resulting in a blue complex.

- Statement iv is incorrect; glycogen is a highly branched polysaccharide, not linear, which allows for rapid mobilization of glucose when needed.

Thus, the correct statements are those in Option B: i and iii.

Topic in NCERT: Polysaccharides

Line in NCERT: "polysaccharides are long chains of sugars. they are threads (literally a cotton thread) containing different monosaccharides as building blocks. for example, cellulose is a polymeric polysaccharide consisting of only one type of monosaccharide i.e., glucose. cellulose is a homopolymer. starch is a variant of this but present as a store house of energy in plant tissues."

To analyze the statements:

- Statement i is correct; it describes the slow reaction rate in the absence of an enzyme.

- Statement ii is also correct; it accurately describes the function of carbonic anhydrase and its dramatic acceleration of the reaction rate.

- Statement iii is accurate; it notes that the pathway from glucose to pyruvic acid consists of ten enzyme-catalyzed reactions.

- Statement iv is incorrect; under anaerobic conditions, lactic acid is produced in skeletal muscle, not pyruvic acid.

Therefore, the correct answer, which includes statements i, ii and iii, is Option B.

Topic in NCERT: Enzymes and metabolic pathways

Line in NCERT: "in the absence of any enzyme this reaction is very slow, with about 200 molecules of h2co3 being formed in an hour. however, by using the enzyme present within the cytoplasm called carbonic anhydrase, the reaction speeds dramatically with about 600,000 molecules being formed every second."

"this very metabolic pathway with one or two additional reactions gives rise to a variety of metabolic end products. in our skeletal muscle, under anaerobic conditions, lactic acid is formed. under normal aerobic conditions, pyruvic acid is formed."

"glucose becomes pyruvic acid through ten different enzyme catalysed metabolic reactions."

To determine the correct statements:

• Statement i is incorrect because lipids are generally water insoluble, not soluble.
• Statement ii is correct as it accurately describes the types of fatty acids.
• Statement iii is incorrect because glycerol is not a simple sugar; it is a trihydroxy alcohol (trihydroxy propane) that combines with fatty acids to form triglycerides.
• Statement iv is correct as phospholipids are indeed found in cell membranes and contain phosphorus.

Thus, the correct statements are ii and iv, making Option A the right choice.

Topic in NCERT: Fats and oils (lipids)

Line in NCERT: "fatty acids could be saturated (without double bond) or unsaturated (with one or more c=c double bonds)."
"these are phospholipids. they are found in cell membrane."

• Statement i is correct because nucleic acids are indeed made up of polynucleotides that include ribose in RNA and deoxyribose in DNA.
• Statement ii is incorrect; the building blocks of nucleic acids are nucleotides, not amino acids (which are the building blocks of proteins).
• Statement iii is correct as it accurately lists the nitrogenous bases found in nucleic acids.
• Statement iv is incorrect; DNA contains deoxyribose, while RNA contains ribose.

Topic in NCERT: Nucleic acids

Line in NCERT: "for nucleic acids, the building block is a nucleotide. the sugar found in polynucleotides is either ribose (a monosaccharide pentose) or 2'-deoxyribose. a nucleic acid containing deoxyribose is called deoxyribonucleic acid (dna) while that which contains ribose is called ribonucleic acid (rna)."

- Statement i is correct because all amino acids indeed have an amino group (-NH2) and a carboxyl group (-COOH) attached to the same α-carbon.

- Statement ii is  correct as Based on the nature of R group there are many amino acids. However, those which occur in proteins are only of twenty  types

- Statement iii is correct because the R group (side chain) varies among amino acids and determines their unique chemical properties.

- Statement iv is incorrect; while amino acids can be classified as acidic or basic, they can also be neutral and aromatic, making this statement false.

Thus, the correct statements are i, ii, and iii, leading to the answer being Option A.

Topic in NCERT: Amino acids

Line in NCERT: "amino acids are organic compounds containing an amino group and an acidic group as substituents on the same carbon i.e., the α-carbon. hence, they are called α-amino acids. they are substituted methanes. there are four substituent groups occupying the four valency positions. these are hydrogen, carboxyl group, amino group and a variable group designated as r group. based on the nature of r group there are many amino acids. however, those which occur in proteins are only of twenty types."

- Statement i is correct because enzymes do require cofactors to be catalytically active, and the protein part without the cofactor is indeed called the apoenzyme.

- Statement ii is incorrect; prosthetic groups are tightly bound to the apoenzyme, not loosely associated.

- Statement iii is correct because coenzymes are indeed transiently associated with the apoenzyme and are often derived from vitamins, such as NAD from niacin.

- Statement iv is correct as certain enzymes do require metal ions, which are essential for their catalytic activity, forming coordination bonds at the active site.

Thus, the correct combination of statements is i, iii, and iv, corresponding to Option C.

Topic in NCERT: Co-factors

Line in NCERT: "enzymes are composed of one or several polypeptide chains. however, there are a number of cases in which non-protein constituents called co-factors are bound to the enzyme to make the enzyme catalytically active. in these instances, the protein portion of the enzymes is called the apoenzyme. three kinds of cofactors may be identified: prosthetic groups, co-enzymes and metal ions."

"prosthetic groups are organic compounds and are distinguished from other cofactors in that they are tightly bound to the apoenzyme."

"co-enzymes are also organic compounds but their association with the apoenzyme is only transient, usually occurring during the course of catalysis."

"a number of enzymes require metal ions for their activity which form coordination bonds with side chains at the active site and at the same time form one or more coordination bonds with the substrate."

"catalytic activity is lost when the co-factor is removed from the enzyme which testifies that they play a crucial role in the catalytic activity of the enzyme."

Transferases are enzymes that facilitate the transfer of functional groups from one substrate to another, which is essential for various metabolic processes.

Topic in NCERT: Classification and nomenclature of enzymes

Line in NCERT: "transferases: enzymes catalysing a transfer of a group, g (other than hydrogen) between a pair of substrate s and s' e.g., s-g+s' → s+s'- g"

Topic in NCERT: Concentration of Substrate

Line in NCERT: "when the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as competitive inhibitor. due to its close structural similarity with the substrate, the inhibitor competes with the substrate for the substrate-binding site of the enzyme."

To determine which statements are correct, let's analyze each one:

- Statement i: This statement describes the initial binding of the substrate to the enzyme's active site, which is accurate as enzymes typically have specific active sites that fit their substrates (the "lock and key" model).

- Statement ii: This statement is also correct. After the substrate binds, the enzyme undergoes an "induced fit," altering its shape for a tighter fit around the substrate.

- Statement iii: This statement correctly describes the formation of the enzyme-product complex, where the active site facilitates the breaking of chemical bonds in the substrate.

- Statement iv: This statement is incorrect. Enzymes are not permanently altered after the reaction; they can be reused to catalyze additional reactions.

Thus, the correct statements are i, ii, and iii, leading to the correct answer being Option D.

Topic in NCERT: Enzyme action and catalysis

Line in NCERT: "1. first, the substrate binds to the active site of the enzyme, fitting into the active site. 2. the binding of the substrate induces the enzyme to alter its shape, fitting more tightly around the substrate. 3. the active site of the enzyme, now in close proximity of the substrate breaks the chemical bonds of the substrate and the new enzyme- product complex is formed."

- The Assertion (A) is correct. The acid insoluble fraction does indeed consist of proteins, nucleic acids, polysaccharides, and lipids, and these are classified as macromolecules except for lipids, which have unique characteristics despite their molecular weight.

- The Reason (R) is incorrect. Lipids are not classified as macromolecules because they are not polymers. While many biological macromolecules (like proteins, nucleic acids, and polysaccharides) are polymers made of repeating monomer units, lipids do not have a repeating unit structure. They are macromolecules only in the general sense of being large molecules, not because they are polymeric.

Also, not all lipids have molecular weights below 800 Da—some complex lipids, such as phospholipids or triglycerides, can have higher molecular weights.

Topic in NCERT: Biomacromolecules

Line in NCERT: "the acid insoluble fraction, has only four types of organic compounds i.e., proteins, nucleic acids, polysaccharides and lipids."